public void IncreaseHoursbyPbtTest()
        {
            var node = new ProcessNode();

            Assert.IsTrue(node.IncreaseHoursbyPbt(0).PlannedCompletionTime == node.PlannedBeginTime);
            node.PlannedBeginTime = DateTime.Now;

            Assert.IsTrue(node.IncreaseHoursbyPbt(0).PlannedCompletionTime == node.PlannedBeginTime);

            Assert.IsTrue(node.IncreaseHoursbyPbt(1).PlannedCompletionTime == node.PlannedBeginTime.Value.AddHours(1));
            node.PlannedBeginTime = null;

            Assert.IsTrue(node.IncreaseHoursbyPbt(1).PlannedCompletionTime == node.PlannedCompletionTime);
        }